Method for sampling and testing data centers for metallic particulates

ABSTRACT

The present invention is drawn to methods for sampling and/or testing for the presence of whisker-like metallic particulates in data centers or computer rooms. For example, a method for discovering the presence of an undesired whisker-like metallic particulate in a data center is disclosed comprising providing a tool having a conductive adhesive portion wherein the conductive adhesive portion is capable of capturing and retaining the whisker-like metallic particulates in their fragile condition, locating a surface of the data center where metallic particulates may be present, extracting from the surface any whisker-like metallic particulates present in substantially their fragile condition using the tool, and confirming with an electron microscope whether or not any whisker-like metallic particulates are present on the conductive adhesive portion of the tool.

FIELD OF THE INVENTION

The present invention is drawn to methods for sampling and/or testingdata centers or computer rooms for fragile whisker-like metallicparticulates.

BACKGROUND OF THE INVENTION

For many years, the electronics industry has been aware of the threatposed by zinc whisker or zinc needle growth on zinc-electroplatedsurfaces. As technology has advanced, and processors, power sources, andthe like have become increasingly smaller, a growing concern hasdeveloped with respect to these whisker-like conductive contaminants.This has been particularly a problem in the so-called “computer room”where zinc electroplated floor tiles are used to form grounds forcomputer components, as well as provide a convenient path fortechnicians to run cables and wires. On the bottom of some of thesefloor tiles, as well as in other locations, these whisker-like growthscan form.

Generally, it is known that tin, zinc, and cadmium plating can growwhiskers. This type of plating is frequently used as corrosionprotection for steel electronic enclosures. Some have proposed thatcertain electroplating processes impart internal stress in these metals,setting the stage for whisker growth. Though tin is more susceptible towhisker formation than either cadmium or zinc, zinc plating is morecommon in computer rooms and data center. This is because zinc platingis often applied to electronic enclosures, structural elements, andother equipment made of high strength, low alloy steel. Zinc whiskersare formed from metal surfaces coated with zinc in a galvanizationprocess to help protect them from corrosion. The zinc whiskers generallycan be described as zinc filaments extending from these treatedsurfaces. They are normally only a few microns in width, but can beseveral hundred to over a thousand microns in length.

The first zinc-plated enclosures in use with computer equipmentpresented some whisker problems, but these problems were easily remedieddue to the large circuitry spacing and higher voltages used in thesystems. However, as technology has become more sophisticated, zincwhiskers are creating a greater problem. For example, low voltages asare present in more modern systems are not capable of burning offmetallic whiskers in a quick manner. It is also suspected that higheroperating temperatures of systems as a whole encourage the incubationand growth of whisker-like particulates.

Zinc whisker growth has been found on sub-racks, switches, card cages,floor tiles, frames, internet routers, and other electroplated surfaces.They can also be found growing from certain computer hardware. However,if these whisker-like particulates become airborne, they can be foundanywhere in a computer room or computer data center, or can be carriedinto a data center from an external source. Not all electroplatedsurfaces appear to exhibit whisker growth, and not all of such surfacesdevelop the problem at the same rate. Thus, it is suspected that whiskergrowth is affected to some extent by the environment in combination withthe electroplated surface.

As previously stated, floor tiles are a location where zinc whiskergrowth is particularly prevalent. This is partly because these floortiles have large surface areas, and are often disturbed during normalactivity in a computer room or data center, e.g., removed by techniciansor disturbed by running cable, etc. Additionally, raised floor tileconstruction used in most computer rooms is utilized as a duct forsupplying necessary airflow to computer components. Because of thisactivity and airflow, zinc whiskers can easily be dislodged and carriedto the hardware. Additionally, floor tiles are often dragged across thetop of each other as they are removed from a floor grid, spreading thecontamination throughout the room.

A reason that zinc whiskers (or other undesired metallic particulates)cause failures or other problems in computer rooms is because they areconductive contaminants, and can actually cause shorts on circuit boardcards, power supplies, or other electronic components. As computercircuitry has become smaller, and voltages have decreased generally,short metallic whiskers can span two electrically isolated features on acircuit board. Such a span can, for example, misdirect current causingunforeseen problems. Though the growth of zinc whiskers is not new,their ability to impact hardware reliability has been increased bydenser geometries of the newer technologies.

Metallic particulates such as zinc whiskers have been discovered byvisual inspection and/or by the wiping of an area with a swatch. Thus,in the prior art, the presence of zinc whiskers in data centers havebeen discovered using less precise methods than those of the presentinvention. Some of these prior art methods do not provide the detailedinformation sometimes necessary for determining the best approach forremediation. For example, with respect to wipe sampling, a wet wipe isused to sample an area. The wipe can then be sealed in a plastic bag andsent to an environmental lab where tests are conducted to determinewhether zinc is present on the wipe. However, with this method, the labis not always able to determine if the zinc is in the form of a zincwhisker. Further, even if such a determination can be made, the lab maynot be able to accurately determine the length of the zinc whisker, thesurface properties of the zinc whisker, or the concentration of zincwhiskers sampled from a given area.

SUMMARY OF THE INVENTION

The present inventors have determined that providing a method ofsampling and/or testing for the presence of fragile whisker-likemetallic particulates in a data center, while maintaining the sample inits fragile state, would be an advancement in the art. Thus, the presentinvention is drawn to methods for sampling and/or testing data centersor computer rooms for the presence of fragile whisker-like metallicparticulates in a data center. A first method of sampling for thepresence of fragile whisker-like metallic particulates in a data centeris disclosed. There the sampling steps comprise providing a tool capableof capturing and retaining the whisker-like metallic particulates intheir fragile condition, wherein the tool comprises an adhesive portionfor extracting the whisker-like particulates, wherein the adhesiveportion is a conductive adhesive, locating a surface of the data centerwhere metallic particulates may be present, and extracting from thesurface any whisker-like metallic particulates present in theirsubstantially fragile condition.

Additionally, a method for discovering the presence of an undesiredwhisker-like metallic particulate in a data center is disclosedcomprising locating a surface of the data center where the presence of awhisker-like metallic particulate is suspected, extracting anywhisker-like metallic particulate that may be present on the surfaceonto an adhesive intermediate substrate, wherein the adhesiveintermediate substrate is conductive, and confirming whether or not anywhisker-like metallic particulates are present on the adhesiveintermediate substrate.

In a more detailed aspect of the invention, a method for discovering thepresence of an undesired whisker-like metallic particulate in a datacenter is disclosed. This method comprises the steps of providing a toolhaving a conductive adhesive portion wherein the conductive adhesiveportion is capable of capturing and retaining the whisker-like metallicparticulates in their fragile condition, locating a surface of the datacenter where metallic particulates may be present, extracting from thesurface any whisker-like metallic particulates present in substantiallytheir fragile condition using the tool, and confirming with an electronmicroscope whether or not any whisker-like metallic particulates arepresent on the conductive adhesive portion of the tool.

DETAILED DESCRIPTION OF THE INVENTION

Before the present invention is disclosed and described, it is to beunderstood that this invention is not limited to the particular processsteps and materials disclosed herein because such process steps andmaterials may vary somewhat. It is also to be understood that theterminology used herein is used for the purpose of describing particularembodiments only. The terms are not intended to be limiting because thescope of the present invention is intended to be limited only by theappended claims and equivalents thereof.

It must be noted that, as used in this specification and the appendedclaims, the singular forms “a,” “an,” and “the” include plural referentsunless the content clearly dictates otherwise.

“Data center” or “computer room” is intended to include any room where asubstantial amount of computer equipment is present, such as, forexample, an internet server room or a large company computer room.

“Whisker-like metallic particulate” includes any metal particulategrowth that is elongated along an axis. Typically, these particulatesgrow from electroplated metal surfaces, and can break off becomingmobile. Zinc, tin, and cadmium plating can form these whiskers, thoughany other plated metal may also form whisker-like protrusions under theright conditions.

“Adhesive” shall include any material that provides more adhesivestrength than the adhesion provided by water on a cloth or papermaterial (such as with a wet wipe), and are preferably substantiallymore adhesive. Additionally, it is preferred that the adhesive substancebe a material not significantly prone to evaporative tendencies overshort periods of time. Examples of adhesives can include materials usedfor glues and tapes. An adhesive carbon conductive material can also beused.

With these definitions in mind, several methods are disclosed hereinthat are effective for sampling and/or testing for the presence ofwhisker-like metallic particulates, including, for example, zincwhiskers. With respect to a first method, a method of sampling for thepresence of fragile whisker-like metallic particulates in a data centeris disclosed. This method comprises the steps of providing a toolcapable of capturing and retaining the whisker-like metallicparticulates in their fragile condition, locating a surface of the datacenter where metallic particulates may be present, and extracting fromthe surface any whisker-like metallic particulates present insubstantially their fragile condition.

With this method, the tool can comprise an adhesive portion forextracting the whisker-like metallic particulates. Additionally, theadhesive portion can be a conductive material such as, for example, acarbon conductive material. One reason that it may be desirous to use aconductive material is because if any analysis of the sample is to occurwith the aid of an electron microscope, then there need not beadditional preparation required to view the sample. If, for example, acellophane adhesive was used to extract the sample, then an intermediatestep of carefully transferring the sample to a conductive substratewould be required prior to electron microscope viewing, though such anembodiment is also within the scope of the invention.

One technique that can be used to extract a sample from a surface caninclude gently pressing an adhesive portion of a tool on the surface tobe sampled. Further, it may be desired to extract the sample such that adensity of the whisker-like metallic particulates over a predeterminedsurface area can be determined. If the desire is simply to determinewhether or not zinc whiskers are present in a data center or computerroom, then any area can be sampled. However, for a more controlledanalysis, the location(s) of the sample(s) taken from the room should berecorded.

Once the surface is sampled, a further step of protecting the samplefrom substantial contamination prior to testing the sample for thepresence of whisker-like metallic particulates can be carried out. Forexample, one can take steps to ensure that the sample is stored in anenclosure such that the adhesive portion does not contact the enclosure.Such an enclosure can be a box having support structures for holding ahandle portion of the tool, while suspending the adhesive portion withinthe box. Additionally, though not required, the tool can be configuredto be modular such that the adhesive portion is removable from a handleportion. For example, the adhesive portion can be a conductive carbonadhesive in the shape of a disc that can be removed from an elongatedhandle portion of the tool. Thus, viewing of the conductive carbonadhesive with an electron microscope or other analytical equipment canoccur without the presence of the handle. Though this method can be usedto sample any fragile whisker-like metallic particulate, typically,these particulates are selected from the group consisting of zincwhiskers, tin whiskers, and cadmium whiskers. If sampling a computerroom or data center, a typical place that one might sample is a floortile surface, particularly, the bottom of a floor tile.

If a more thorough sampling is necessary, additional sampling steps canbe taken. Such steps can include locating a second surface of the datacenter wherein whisker-like metallic particulates may be present,providing a second tool capable of capturing and retaining thewhisker-like metallic particulates in their fragile condition, andextracting from the second surface any whisker-like metallicparticulates present in their substantially fragile condition.

Alternatively, a method for discovering the presence of an undesiredwhisker-like metallic particulate in a data center is also disclosed.With this method, several steps can be carried out including locating asurface of the data center where the presence of a whisker-like metallicparticulate is suspected, extracting any whisker-like metallicparticulate that may be present on the surface onto an adhesiveintermediate substrate, and confirming whether or not any whisker-likemetallic particulates are present on the intermediate substrate.

Though not required, in this embodiment, it is preferred that the stepof extracting any whisker-like metallic particulates is done such thatthe particulates are substantially retained in their fragile condition.Again, if the desire is to use an electron microscope to confirm orreject the presence of the whisker-like metallic particulates, theintermediate substrate can be a conductive adhesive, such as a carbonconductive adhesive. If such a conductive adhesive is used, then anadditional step of slide preparation for use with an electron microscopecan be avoided. Appropriate electron microscopes that can be usedinclude scanning electron microscopes, field emission electronmicroscopes, and transmission electron microscopes, to name a few.

If one is viewing whisker-like metallic particulates with an electronmicroscope (or other microscopic viewing device), then the step ofcharacterizing any particulates present with respect to geometry,surface properties, and/or density can be carried out. This can be doneto provide more information to an analyst regarding the particulatespresent in a data center or computer room. In addition, the whisker-likemetallic particulates can also be characterized using energy dispersivespectroscopy (EDS). One reason that the use of carbon conducive materialis a good material for use during sampling of the computer room or datacenter is that it provides peaks (carbon) that do not interfere withzinc peaks if EDS is used for analysis of the sample.

In another more detailed aspect of the invention, a method fordiscovering the presence of an undesired whisker-like metallicparticulate in a data center is disclosed comprising the steps ofproviding a tool having a conductive adhesive portion wherein theconductive adhesive portion is capable of capturing and retaining thewhisker-like metallic particulates in their fragile condition, locatinga surface of the data center where metallic particulates may be present,extracting from the surface any whisker-like metallic particulatespresent in their substantially fragile condition using the tool, andconfirming with an electron microscope whether or not any whisker-likemetallic particulates are present on the conductive adhesive portion ofthe tool. Optionally, the step of characterizing any whisker-likemetallic particulates confirmed to be present for geometry, surfaceproperties, and density can also be carried out. If the tool is modular,the conductive adhesive portion can be removed from the tool prior tothe step of confirming the presence of metallic particulates.

Though the methods of the present invention are drawn primarily to thesampling, detection, and characterization of whisker-like metallicparticulates, if such particulates are discovered, then remediationsteps should be taken. For example, if zinc whisker growth is identifiedon a floor tile, extreme caution should be exercised to avoid making theproblem worse, e.g., spreading the zinc whiskers throughout the datacenter or computer room. One remediation approach is to replace allfloor tiles, with selective encapsulation of inaccessible tiles. Thisprocedure can be an extremely delicate and labor-intensive procedure,and if not done properly, can cause the problem to become worse throughinadvertent spreading. If a floor tile or raised floor is grosslycontaminated, then a detailed plan may be necessary to reduce thelikelihood of increased problems associated with remediation. Forexample, areas of greatest contamination should be identified using themethods of the present invention. Then, with this knowledge, appropriateequipment can be moved or affected areas can be isolated from affectedareas. In any event, care should be taken not to disturb any loosewhiskers during remediation cleanup.

An example of several remediation steps that can be taken are describedherein. First, all equipment that can be powered down and removed fromthe data center should be removed. Next, as many air conditioning unitsthat can be powered down should also be powered down. The remainingequipment can then be covered with plastic barrier tents, such as, forexample, between the ceiling and the floor. If there is still airflowunder the floor, under-floor barriers can also be created. This is animportant step as these barriers will protect the equipment fromzinc-laden airflow during the replacement process. The affected panelscan now more safely be carefully lifted and removed from the room. Thisshould be done without sliding or otherwise shaking the tiles. Once thepanels are safely within plastic bags, they can be removed from theroom. The under-floor area can be cleaned with a vacuum, wet wiping, orother known procedures. New panels (not subject to whisker-like metallicgrowth) can now be put in place and the room restored to its originalcondition.

While the invention has been described with reference to certainpreferred embodiments, those skilled in the art will appreciate thatvarious modifications, changes, omissions, and substitutions can be madewithout departing from the spirit of the invention. It is thereforeintended that the invention be limited only by the scope of the appendedclaims.

We claim:
 1. A method of sampling for the presence of fragilewhisker-like metallic particulates in a data center comprising: (a)providing a tool capable of capturing and retaining the whisker-likemetallic particulates in their fragile condition, wherein the toolcomprises an adhesive portion for extracting the whisker-likeparticulates, wherein the adhesive portion is a conductive adhesive; (b)locating a surface of the data center where metallic particulate may bepresent; and (c) extracting from the surface any whisker-like metallicparticulates present in substantially their fragile condition.
 2. Amethod as in claim 1 wherein the conductive adhesive is a carbonconductive material.
 3. A method as in claim 1 wherein the step ofextracting is carried out by pressing the adhesive portion on thesurface.
 4. A method as in claim 1 wherein the step of extractingfurther comprises sampling a density of the whisker-like metallicparticulates over a predetermined surface area.
 5. A method as in claim1 further comprising the step of recording a location of the surface. 6.A method as in claim 1 further comprising the step of storing a samplesuch that the sample is protected from substantial contamination.
 7. Amethod as in claim 6 wherein the sample is stored in an enclosure suchthat the adhesive portion does not contact the enclosure.
 8. A method asin claim 1 wherein the tool is modular and the adhesive portion isremovable from a handle portion.
 9. A method as in claim 1 wherein thefragile whisker-like metallic particulates are selected from the groupconsisting of zinc whiskers, cadmium whiskers, tin whiskers, andaluminum whiskers.
 10. A method as in claim 1 further comprising thesteps of: (a) locating a second surface of the data center whereinwhisker-like metallic particulates may be present; (b) providing asecond conductive adhesive tool capable of capturing and retaining thewhisker-like metallic particulates in their fragile condition; and (c)extracting from the second surface any whisker-like metallicparticulates present in substantially their fragile condition.
 11. Amethod as in claim 1 wherein the surface is on a floor tile.
 12. Amethod as in claim 11 wherein the step of extracting is from a bottomside of the floor tile.
 13. A method for discovering a presence of anundesired whisker-like metallic particulate in a data center comprising:(a) locating a surface of the data center where the presence of awhisker-like metallic particulate is suspected; (b) extracting anywhisker-like metallic particulate that may be present on the surfaceonto an adhesive intermediate substrate, wherein the adhesiveintermediate substrate is conductive; and (c) confirming whether or notany whisker-like metallic particulates are present on the adhesiveintermediate substrate.
 14. A method as in claim 13 wherein theintermediate substrate comprises conductive carbon.
 15. A method as inclaim 13 wherein the step of confirming whether or not any whisker-likemetallic particulates are present is done with an electron microscope.16. A method as in claim 15 wherein the electron microscope is selectedfrom the group consisting of a scanning electron microscope, a fieldemission electron microscope, and a transmission electron microscope.17. A method as in claim 13 wherein the whisker-like metallicparticulates are selected from the group consisting of zinc whiskers,tin whiskers, cadmium whiskers, aluminum whiskers, and combinationsthereof.
 18. A method as in claim 13 wherein the step of confirmingwhether or not any whisker-like metallic particulates are presentfurther comprises the step of characterizing any whisker-like metallicparticulates present with respect to geometry, surface properties, anddensity.
 19. A method as in claim 13 further comprising the step ofcharacterizing the whisker-like metallic particulates using energydispersive spectroscopy (EDS).
 20. A method for discovering a presenceof an undesired whisker-like metallic particulate in a data centercomprising: (a) providing a tool having a conductive adhesive portion,said conductive adhesive portion being capable of capturing andretaining the whisker-like metallic particulates in their fragilecondition; (b) locating a surface of the data center where metallicparticulates may be present; (c) extracting from the surface anywhisker-like metallic particulates present in substantially theirfragile condition using the tool; and (d) confirming with an electronmicroscope whether or not any whisker-like metallic particulates arepresent on the conductive adhesive portion of the tool.
 21. A method asin claim 20 further comprising the step of characterizing anywhisker-like metallic particulates confirmed to be present for geometry,surface properties, and density.
 22. A method as in claim 13 wherein thestep of extracting any whisker-like metallic particulates is done suchthat the whisker-like metallic particulates are substantially retainedin their fragile condition.